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Can life survive a star’s death? Webb telescope can reveal the answer

When stars like our sun die, all that remains is an exposed core — a white dwarf. A planet orbiting a white dwarf presents a promising opportunity to determine if life can survive the death of its star, according to Cornell University researchers.

In a study published in the Astrophysical Journal Letters, they show how NASA’s upcoming James Webb Space Telescope could find signatures of life on Earth-like planets orbiting white dwarfs.

A planet orbiting a small star produces strong atmospheric signals when it passes in front, or “transits,” its host star. White dwarfs push this to the extreme: They are 100 times smaller than our sun, almost as small as Earth, affording astronomers a rare opportunity to characterize rocky planets.

“If rocky planets exist around white dwarfs, we could spot signs of life on them in the next few years,” said corresponding author Lisa Kaltenegger, associate professor of astronomy in the College of Arts and Sciences and director of the Carl Sagan Institute.

Co-lead author Ryan MacDonald, a research associate at the institute, said the James Webb Space Telescope, scheduled to launch in October 2021, is uniquely placed to find signatures of life on rocky exoplanets.

“When observing Earth-like planets orbiting white dwarfs, the James Webb Space Telescope can detect water and carbon dioxide within a matter of hours,” MacDonald said. “Two days of observing time with this powerful telescope would allow the discovery of biosignature gases, such as ozone and methane.”

The discovery of the first transiting giant planet orbiting a white dwarf (WD 1856+534b), announced in a separate paper — led by co-author Andrew Vanderburg, assistant professor at the University of Wisconsin, Madison — proves the existence of planets around white dwarfs. Kaltenegger is a co-author on this paper, as well.

This planet is a gas giant and therefore not able to sustain life. But its existence suggests that smaller rocky planets, which could sustain life, could also exist in the habitable zones of white dwarfs.

“We know now that giant planets can exist around white dwarfs, and evidence stretches back over 100 years showing rocky material polluting light from white dwarfs. There are certainly small rocks in white dwarf systems,” MacDonald said. “It’s a logical leap to imagine a rocky planet like the Earth orbiting a white dwarf.”

The researchers combined state-of-the-art analysis techniques routinely used to detect gases in giant exoplanet atmospheres with the Hubble Space Telescope with model atmospheres of white dwarf planets from previous Cornell research.

NASA’s Transiting Exoplanet Survey Satellite is now looking for such rocky planets around white dwarfs. If and when one of these worlds is found, Kaltenegger and her team have developed the models and tools to identify signs of life in the planet’s atmosphere. The Webb telescope could soon begin this search.

The implications of finding signatures of life on a planet orbiting a white dwarf are profound, Kaltenegger said. Most stars, including our sun, will one day end up as white dwarfs.

“What if the death of the star is not the end for life?” she said. “Could life go on, even once our sun has died? Signs of life on planets orbiting white dwarfs would not only show the incredible tenacity of life, but perhaps also a glimpse into our future.”

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Portable DNA device can detect tree pests in under two hours

Asian gypsy moths feed on a wide range of important plants and trees. White pine blister rust can kill young trees in only a couple of years. But it’s not always easy to detect the presence of these destructive species just by looking at spots and bumps on a tree, or on the exterior of a cargo ship.

Now a new rapid DNA detection method developed at the University of British Columbia can identify these pests and pathogens in less than two hours, without using complicated processes or chemicals — a substantial time savings compared to the several days it currently takes to send samples to a lab for testing.

“Sometimes, a spot is just a spot,” explains forestry professor Richard Hamelin, who designed the system with collaborators from UBC, Natural Resources Canada and the Canadian Food Inspection Agency. “Other times, it’s a deadly fungus or an exotic bug that has hitched a ride on a shipping container and has the potential to decimate local parks, forests and farms. So you want to know as soon as possible what you’re looking at, so that you can collect more samples to assess the extent of the invasion or begin to formulate a plan of action.”

Hamelin’s research focuses on using genomics to design better detection and monitoring methods for invasive pests and pathogens that threaten forests. For almost 25 years, he’s been looking for a fast, accurate, inexpensive DNA test that can be performed even in places, like forests, without fast Internet or steady power supply.

He may have found it. The method, demonstrated in a preview last year for forestry policymakers in Ottawa, is straightforward. Tiny samples like parts of leaves or branches, or insect parts like wings and antennae, are dropped into a tube and popped into a small, battery-powered device (the Franklin thermo cycler, made by Philadelphia-based Biomeme). The device checks to see if these DNA fragments match the genomic material of the target species and generates a signal that can be visualized on a paired smartphone.

“With this system, we can tell with nearly 100 per cent accuracy if it is a match or not, if we’re looking at a threatening invasive species or one that’s benign,” said Hamelin. “We can analyze up to nine samples from the same or different species at a time, and it’s all lightweight enough — the thermocycler weighs only 1.3 kilos — to fit into your backpack with room to spare.”

The method relies on PCR testing, the method that is currently also the gold standard for COVID-19. PCR testing effectively analyzes even tiny amounts of DNA by amplifying (through applying heating and cooling cycles) a portion of the genetic material to a level where it can be detected.

Hamelin’s research was supported by Genome Canada, Genome BC and Genome Quebec and published in PLOS One. The UBC team, including lead author Arnaud Capron, tested this approach on species such as the Asian gypsy moth, white pine blister rust and sudden oak death pathogen, which are listed among the most destructive invasive pests worldwide.

“Our forestry, agriculture and horticulture are vital industries contributing billions of dollars to Canada’s economy so it’s essential that we protect them from their enemies,” added Hamelin. “With early detection and steady surveillance, we can ensure that potential problems are nipped, so to speak, in the bud.”

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Ways to keep buildings cool with improved super white paints

A research team led by UCLA materials scientists has demonstrated ways to make super white paint that reflects as much as 98% of incoming heat from the sun. The advance shows practical pathways for designing paints that, if used on rooftops and other parts of a building, could significantly reduce cooling costs, beyond what standard white ‘cool-roof’ paints can achieve.

The findings, published online in Joule, are a major and practical step towards keeping buildings cooler by passive daytime radiative cooling — a spontaneous process in which a surface reflects sunlight and radiates heat into space, cooling down to potentially sub-ambient temperatures. This can lower indoor temperatures and help cut down on air conditioner use and associated carbon dioxide emissions.

“When you wear a white T-shirt on a hot sunny day, you feel cooler than if you wore one that’s darker in color — that’s because the white shirt reflects more sunlight and it’s the same concept for buildings,” said Aaswath Raman, an assistant professor of materials science and engineering at UCLA Samueli School of Engineering, and the principal investigator on the study. “A roof painted white will be cooler inside than one in a darker shade. But those paints also do something else: they reject heat at infrared wavelengths, which we humans cannot see with our eyes. This could allow buildings to cool down even more by radiative cooling.”

The best performing white paints currently available typically reflect around 85% of incoming solar radiation. The remainder is absorbed by the chemical makeup of the paint. The researchers showed that simple modifications in a paint’s ingredients could offer a significant jump, reflecting as much as 98% of incoming radiation.

Current white paints with high solar reflectance use titanium oxide. While the compound is very reflective of most visible and near-infrared light, it also absorbs ultraviolet and violet light. The compound’s UV absorption qualities make it useful in sunscreen lotions, but they also lead to heating under sunlight — which gets in the way of keeping a building as cool as possible.

The researchers examined replacing titanium oxide with inexpensive and readily available ingredients such as barite, which is an artist’s pigment, and powered polytetrafluoroethylene, better known as Teflon. These ingredients help paints reflect UV light. The team also made further refinements to the paint’s formula, including reducing the concentration of polymer binders, which also absorb heat.

“The potential cooling benefits this can yield may be realized in the near future because the modifications we propose are within the capabilities of the paint and coatings industry,” said UCLA postdoctoral scholar Jyotirmoy Mandal, a Schmidt Science Fellow working in Raman’s research group and the co-corresponding author on the research.

Beyond the advance, the authors suggested several long-term implications for further study, including mapping where such paints could make a difference, studying the effect of pollution on radiative cooling technologies, and on a global scale, if they could make a dent on the earth’s own ability to reflect heat from the sun.

The researchers also noted that many municipalities and governments, including the state of California and New York City, have started to encourage cool-roof technologies for new buildings.

“We hope that the work will spur future initiatives in super-white coatings for not only energy savings in buildings, but also mitigating the heat island effects of cities, and perhaps even showing a practical way that, if applied on a massive, global scale could affect climate change,” said Mandal, who has studied cooling paint technologies for several years. “This would require a collaboration among experts in diverse fields like optics, materials science and meteorology, and experts from the industry and policy sectors.”

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White dwarfs reveal new insights into the origin of carbon in the universe

A new analysis of white dwarf stars supports their role as a key source of carbon, an element crucial to all life, in the Milky Way and other galaxies.

Approximately 90 percent of all stars end their lives as white dwarfs, very dense stellar remnants that gradually cool and dim over billions of years. With their final few breaths before they collapse, however, these stars leave an important legacy, spreading their ashes into the surrounding space through stellar winds enriched with chemical elements, including carbon, newly synthesized in the star’s deep interior during the last stages before its death.

Every carbon atom in the universe was created by stars, through the fusion of three helium nuclei. But astrophysicists still debate which types of stars are the primary source of the carbon in our own galaxy, the Milky Way. Some studies favor low-mass stars that blew off their envelopes in stellar winds and became white dwarfs, while others favor massive stars that eventually exploded as supernovae.

In the new study, published July 6 in Nature Astronomy, an international team of astronomers discovered and analyzed white dwarfs in open star clusters in the Milky Way, and their findings help shed light on the origin of the carbon in our galaxy. Open star clusters are groups of up to a few thousand stars, formed from the same giant molecular cloud and roughly the same age, and held together by mutual gravitational attraction. The study was based on astronomical observations conducted in 2018 at the W. M. Keck Observatory in Hawaii and led by coauthor Enrico Ramirez-Ruiz, professor of astronomy and astrophysics at UC Santa Cruz.

“From the analysis of the observed Keck spectra, it was possible to measure the masses of the white dwarfs. Using the theory of stellar evolution, we were able to trace back to the progenitor stars and derive their masses at birth,” Ramirez-Ruiz explained.

The relationship between the initial masses of stars and their final masses as white dwarfs is known as the initial-final mass relation, a fundamental diagnostic in astrophysics that integrates information from the entire life cycles of stars, linking birth to death. In general, the more massive the star at birth, the more massive the white dwarf left at its death, and this trend has been supported on both observational and theoretical grounds.

But analysis of the newly discovered white dwarfs in old open clusters gave a surprising result: the masses of these white dwarfs were notably larger than expected, putting a “kink” in the initial-final mass relation for stars with initial masses in a certain range.

“Our study interprets this kink in the initial-final mass relationship as the signature of the synthesis of carbon made by low-mass stars in the Milky Way,” said lead author Paola Marigo at the University of Padua in Italy.

In the last phases of their lives, stars twice as massive as our Sun produced new carbon atoms in their hot interiors, transported them to the surface, and finally spread them into the interstellar medium through gentle stellar winds. The team’s detailed stellar models indicate that the stripping of the carbon-rich outer mantle occurred slowly enough to allow the central cores of these stars, the future white dwarfs, to grow appreciably in mass.

Analyzing the initial-final mass relation around the kink, the researchers concluded that stars bigger than 2 solar masses also contributed to the galactic enrichment of carbon, while stars of less than 1.5 solar masses did not. In other words, 1.5 solar masses represents the minimum mass for a star to spread carbon-enriched ashes upon its death.

These findings place stringent constraints on how and when carbon, the element essential to life on Earth, was produced by the stars of our galaxy, eventually ending up trapped in the raw material from which the Sun and its planetary system were formed 4.6 billion years ago.

“Now we know that the carbon came from stars with a birth mass of not less than roughly 1.5 solar masses,” said Marigo.

Coauthor Pier-Emmanuel Tremblay at University of Warwick said, “One of most exciting aspects of this research is that it impacts the age of known white dwarfs, which are essential cosmic probes to understand the formation history of the Milky Way. The initial-to-final mass relation is also what sets the lower mass limit for supernovae, the gigantic explosions seen at large distances and that are really important to understand the nature of the universe.”

By combining the theories of cosmology and stellar evolution, the researchers concluded that bright carbon-rich stars close to their death, quite similar to the progenitors of the white dwarfs analyzed in this study, are presently contributing to a vast amount of the light emitted by very distant galaxies. This light, carrying the signature of newly produced carbon, is routinely collected by large telescopes to probe the evolution of cosmic structures. A reliable interpretation of this light depends on understanding the synthesis of carbon in stars.

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Sensing internal organ temperature with shining lights

A cheap, biocompatible white powder that luminesces when heated could be used for non-invasively monitoring the temperature of specific organs within the body. Tohoku University scientists conducted preliminary tests to demonstrate the applicability of this concept and published their findings in the journal Scientific Reports.

Thermometers measure temperature at the body’s surface, but clinicians need to be able to monitor and manage core body temperatures in some critically ill patients, such as following head injuries or heart attacks. Until now, this is most often done by inserting a tiny tube into the heart and blood vessels. But scientists are looking for less invasive means to monitor temperature from within the body.

Applied physicist Takumi Fujiwara of Tohoku University and colleagues in Japan investigated the potential of a white powder called zirconia for this purpose.

Zirconia is a synthetic powder that is easily accessible, chemically stable, and non-toxic. When heated, its crystals become excited, releasing electrons. These electrons then recombine with ‘holes’ in the crystal molecular structure, a process that causes the crystals to emit light, or luminesce. Because of this material’s advantageous properties for use in the human body, the scientists wanted to test and see if its luminescence could be used for monitoring temperature.

The team heated zirconia under an ultraviolet lamp, and found that as zirconia’s temperature rose, its luminescence intensified. The same thing happened when a near-infrared laser light was shone on the material. This demonstrated that both heat and light could be used to induce luminescence in zirconia.

The scientists next showed that zirconia luminescence was visible with the naked eye when placed behind a piece of bone and illuminated using a near-infrared laser.

Together, the demonstrations suggest zirconia could potentially monitor internal body temperature by injecting it and then shining a near-infrared laser light on a targeted location, such as the brain. The intensity and longevity of the material’s luminescence will depend on the surrounding temperature.

“While this fundamental study leaves some important issues unresolved, this work is a novel and promising application of [synthetic luminescent substances] in the medical field,” the researchers conclude. Going forward, the researchers hope to discover a method that makes the wavelength of luminescence from zirconia in the region of red to near-infrared since it makes for better transmissibility for human tissues; thus, allowing for clearer information to be obtained.

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Two stars merged to form massive white dwarf

A massive white dwarf star with a bizarre carbon-rich atmosphere could be two white dwarfs merged together according to an international team led by University of Warwick astronomers, and only narrowly avoided destruction.

They have discovered an unusual ultra-massive white dwarf around 150 light years from us with an atmospheric composition never seen before, the first time that a merged white dwarf has been identified using its atmospheric composition as a clue.

The discovery, published today (2 March) in the journal Nature Astronomy, could raise new questions about the evolution of massive white dwarf stars and on the number of supernovae in our galaxy.

This star, named WDJ0551+4135, was identified in a survey of data from the European Space Agency’s Gaia telescope. The astronomers followed up with spectroscopy taken using the William Herschel Telescope, focusing on those white dwarfs identified as particularly massive — a feat made possible by the Gaia mission. By breaking down the light emitted by the star, the astronomers were able to identify the chemical composition of its atmosphere and found that it had an unusually high level of carbon present.

Lead author Dr Mark Hollands, from the University of Warwick Department of Physics, said: “This star stood out as something we had never seen before. You might expect to see an outer layer of hydrogen, sometimes mixed with helium, or just a mix of helium and carbon. You don’t expect to see this combination of hydrogen and carbon at the same time as there should be a thick layer of helium in between that prohibits that. When we looked at it, it didn’t make any sense.”

To solve the puzzle, the astronomers turned detective to uncover the star’s true origins.

White dwarfs are the remains of stars like our own Sun that have burnt out all their fuel and shed their outer layers. Most are relatively lightweight, around 0.6 times the mass of our Sun, but this one weighs in at 1.14 solar masses, nearly twice the average mass. Despite being heavier than our Sun, it is compacted into two-thirds the diameter of Earth.

The age of the white dwarf is also a clue. Older stars orbit the Milky Way faster than younger ones, and this object is moving faster than 99% of the other nearby white dwarfs with the same cooling age, suggesting that this star is older than it looks.

Dr Hollands adds: “We have a composition that we can’t explain through normal stellar evolution, a mass twice the average for a white dwarf, and a kinematic age older than that inferred from cooling. We’re pretty sure of how one star forms one white dwarf and it shouldn’t do this. The only way you can explain it is if it was formed through a merger of two white dwarfs.”

The theory is that when one star in a binary system expands at the end of its life it will envelope its partner, drawing its orbit closer as the first star shrinks. The same will happen when the other star expands. Over billions of years, gravitational wave emission will shrink the orbit further, to the point that the stars merge together.

While white dwarf mergers have been predicted to occur, this one would be particularly unusual. Most of the mergers in our galaxy will be between stars with different masses, whereas this merger appears to be between two similarly sized stars. There is also a limit to how big the resulting white dwarf can be: at more than 1.4 solar masses it is thought that it would explode in a supernova though it may be possible for that these explosions can occur at slightly lower masses, so this star is useful in demonstrating how massive a white dwarf can get and still survive.

Because the merging process restarts the cooling of the star, it is difficult to determine how old it is. The white dwarf probably merged around 1.3 billion years ago but the two original white dwarfs may have existed for many billions of years prior.

It is one of only a handful of merged white dwarfs to be identified so far, and the only one via its composition.

Dr Hollands adds: “There aren’t that many white dwarfs this massive, although there are more than you would expect to see which implies that some of them were probably formed by mergers.

“In the future we may be able to use a technique called asteroseismology to learn about the white dwarf’s core composition from its stellar pulsations, which would be an independent method confirming this star formed from a merger.

“Maybe the most exciting aspect of this star is that it must have just about failed to explode as a supernova — these gargantuan explosions are really important in mapping the structure of the Universe, as they can be detected out to very large distances. However, there remains much uncertainty about what kind of stellar systems make it to the supernova stage. Strange as it may sound, measuring the properties of this ‘failed’ supernova, and future look-alikes, is telling us a lot about the pathways to thermonuclear self-annihilation.”

The research was funded by the European Research Council and the Science and Technologies Facilities Council (STFC) part of UK Research and Innovation (UKRI).

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A faster, easier way to build diamond

It sounds like alchemy: take a clump of white dust, squeeze it in a diamond-studded pressure chamber, then blast it with a laser. Open the chamber and find a new microscopic speck of pure diamond inside.

A new study from Stanford University and SLAC National Accelerator Laboratory reveals how, with careful tuning of heat and pressure, that recipe can produce diamonds from a type of hydrogen and carbon molecule found in crude oil and natural gas.

“What’s exciting about this paper is it shows a way of cheating the thermodynamics of what’s typically required for diamond formation,” said Stanford geologist Rodney Ewing, a co-author on the paper, published Feb. 21 in the journal Science Advances.

Scientists have synthesized diamonds from other materials for more than 60 years, but the transformation typically requires inordinate amounts of energy, time or the addition of a catalyst — often a metal — that tends to diminish the quality of the final product. “We wanted to see just a clean system, in which a single substance transforms into pure diamond — without a catalyst,” said the study’s lead author, Sulgiye Park, a postdoctoral research fellow at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

Understanding the mechanisms for this transformation will be important for applications beyond jewelry. Diamond’s physical properties — extreme hardness, optical transparency, chemical stability, high thermal conductivity — make it a valuable material for medicine, industry, quantum computing technologies and biological sensing.

“If you can make even small amounts of this pure diamond, then you can dope it in controlled ways for specific applications,” said study senior author Yu Lin, a staff scientist in the Stanford Institute for Materials and Energy Sciences (SIMES) at SLAC National Accelerator Laboratory.

A natural recipe

Natural diamonds crystallize from carbon hundreds of miles beneath Earth’s surface, where temperatures reach thousands of degrees Fahrenheit. Most natural diamonds unearthed to date rocketed upward in volcanic eruptions millions of years ago, carrying ancient minerals from Earth’s deep interior with them.

As a result, diamonds can provide insight into the conditions and materials that exist in the planet’s interior. “Diamonds are vessels for bringing back samples from the deepest parts of the Earth,” said Stanford mineral physicist Wendy Mao, who leads the lab where Park performed most of the study’s experiments.

To synthesize diamonds, the research team began with three types of powder refined from tankers full of petroleum. “It’s a tiny amount,” said Mao. “We use a needle to pick up a little bit to get it under a microscope for our experiments.”

At a glance, the odorless, slightly sticky powders resemble rock salt. But a trained eye peering through a powerful microscope can distinguish atoms arranged in the same spatial pattern as the atoms that make up diamond crystal. It’s as if the intricate lattice of diamond had been chopped up into smaller units composed of one, two or three cages.

Unlike diamond, which is pure carbon, the powders — known as diamondoids — also contain hydrogen. “Starting with these building blocks,” Mao said, “you can make diamond more quickly and easily, and you can also learn about the process in a more complete, thoughtful way than if you just mimic the high pressure and high temperature found in the part of the Earth where diamond forms naturally.”

Diamondoids under pressure

The researchers loaded the diamondoid samples into a plum-sized pressure chamber called a diamond anvil cell, which presses the powder between two polished diamonds. With just a simple hand turn of a screw, the device can create the kind of pressure you might find at the center of the Earth.

Next, they heated the samples with a laser, examined the results with a battery of tests, and ran computer models to help explain how the transformation had unfolded. “A fundamental question we tried to answer is whether the structure or number of cages affects how diamondoids transform into diamond,” Lin said. They found that the three-cage diamondoid, called triamantane, can reorganize itself into diamond with surprisingly little energy.

At 900 Kelvin — which is roughly 1160 degrees Fahrenheit, or the temperature of red-hot lava — and 20 gigapascals, a pressure hundreds of thousands of times greater than Earth’s atmosphere, triamantane’s carbon atoms snap into alignment and its hydrogen scatters or falls away.

The transformation unfolds in the slimmest fractions of a second. It’s also direct: the atoms do not pass through another form of carbon, such as graphite, on their way to making diamond.

The minute sample size inside a diamond anvil cell makes this approach impractical for synthesizing much more than the specks of diamond that the Stanford team produced in the lab, Mao said. “But now we know a little bit more about the keys to making pure diamonds.”

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Small altitude changes could cut climate impact of aircraft by up to 59%

Aircraft contrails — the white streaks aircraft leave in the sky — could be as bad for the climate as their carbon dioxide (CO2) emissions. Now, new Imperial College London-led research has found that flight altitude changes of just 2000 feet could lessen their effect.

This, the researchers say, combined with using cleaner aircraft engines, could reduce contrail-caused harm to the climate by up to 90 per cent. Lead author Dr Marc Stettler, of Imperial’s Department of Civil and Environmental Engineering, said: “According to our study, changing the altitude of a small number of flights could significantly reduce the climate effects of aviation contrails. This new method could very quickly reduce the overall climate impact of the aviation industry.”

The research is published in Environmental Science & Technology.

Contrail conundrum

When hot exhaust gases from aircraft meet the cold, low-pressure air of the atmosphere, they produce white streaks in the sky called ‘condensation trails’, or contrails.

The contrail fumes include black carbon particles, which provide surfaces on which moisture condenses to form ice particles. We see this condensation as fluffy white streaks.Most contrails last only a few minutes, but some spread and mix with other contrails and cirrus clouds, forming ‘contrail cirrus’ that linger for up to eighteen hours.

Previous research suggests that contrails and the clouds they help form have as much of a warming impact on the climate as aviation’s cumulative CO2 emissions, because of an effect known as ‘radiative forcing’. This is where the balance is disrupted between radiation coming to earth from the sun and heat emitted from the surface of the earth going out to space, forcing a change in the climate.

The key difference between CO2 and contrails, however, is that while CO2 will have an impact in the atmosphere for hundreds of years, the impact of contrails is short-lived and could therefore quickly be reduced.

Now, Dr Stettler and colleagues have used computer simulations to predict how changing aircraft altitudes might reduce the number of contrails and how long they linger, which would reduce their warming impact. This is because contrails only form and persist in thin layers of the atmosphere that have very high humidity. Because these layers are thin, small changes to flight altitudes would mean that aircraft could avoid these regions, leading to fewer contrails forming.

Using data from Japan’s airspace, they found that just two per cent of flights were responsible for 80 per cent of radiation forcing within the airspace. Dr Stettler said: “A really small proportion of flights are responsible for the vast majority of contrail climate impact, meaning we can focus our attention on them.”

Taking into account the congestion in the airspace above Japan, the team simulated these planes to fly either 2000 feet higher or lower than their actual flight paths and found that the contrail climate forcing could be cut by 59 per cent by altering the altitudes of 1.7 per cent of flights.

The diversion in flight paths caused less than a tenth of a per cent increase in fuel consumption — but, the researchers say, the reduced contrail formation more than offset the CO2 released by the extra fuel.

Dr Stettler suggests that their method of targeting only the few flights that cause the most climate forcing is the best way to avoid hikes in CO2 emissions. He said: “We’re conscious that any additional CO2 released into the atmosphere will have a climate impact stretching centuries into the future, so we’ve also calculated that if we only target flights that wouldn’t emit extra CO¬2, we can still achieve a 20 per cent reduction in contrail forcing.”

The study’s first author, Roger Teoh, also of Imperial’s Department of Civil and Environmental Engineering, said: “Our simulation shows that targeting the few flights that cause the most harmful contrails, as well as making only small altitude changes, could significantly reduce the effect of contrails on global warming.”

Industry impact

The researchers say aircraft engines themselves also play a part in how harmful contrails are. Black carbon particles are produced by incomplete fuel combustion, so new, more efficient engine combustion technology could help to reduce them by around 70 per cent.

This, combined with small altitude changes, could help reduce overall contrail harm by around 90 per cent.

Next, the researchers will refine their simulations to more accurately predict the characteristics and impact of contrails, and to evaluate the wider effects and practicalities of contrail mitigation strategies such as altering flight paths.

Flight data was obtained from Electronic Navigation Research Institute, Japan.

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Steps to Characterize RF Devices with Stimulus-Response Measurements

Download the white paper 3 Steps to Characterize RF Devices with Stimulus-Response Measurements for tips to help you characterize and troubleshoot your RF designs.

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Developing Purpose-Built & Turnkey RF Applications

Developing Purpose-Built & Turnkey RF Applications 

This ThinkRF white paper will explore how SIs can develop a purpose-built, turnkey RF application that lets end-users improve their business and understand the spectrum environment.